Turns GameTicker into an EntitySystem. (#4197)

* GameTicker turned into an EntitySystem

* Turns ClientGameTicker into an EntitySystem, turn NetMessages into events

* Change event names to be more consistent with the rest.

* YAML linter uses the dummy gameticker CVar override.

* Fix game ticker initialization order

* Dummy ticker won't spawn players.

* Fix character creation test

Content.Server/Voting/Managers/VoteManager.cs

@@ -31,7 +31,6 @@ namespace Content.Server.Voting.Managers
         [Dependency] private readonly IGameTiming _timing = default!;
         [Dependency] private readonly IPlayerManager _playerManager = default!;
         [Dependency] private readonly IChatManager _chatManager = default!;
-        [Dependency] private readonly IGameTicker _ticker = default!;
         [Dependency] private readonly IAdminManager _adminMgr = default!;
 
         private int _nextVoteId = 1;